1. Field of the Invention
The present invention relates to image processing, and more particularly to methods and systems for reducing artifacts that are caused by image processing.
2. Description of the Related Art
There are a variety of existing image-processing systems and techniques. Some of these existing systems and techniques use histogram equalization to expand the dynamic range and contrast of an image. In a technique known as adaptive histogram equalization (“AHE”), the image is divided into small portions called “tiles,” and histogram equalization is applied to each tile by using a look-up table. AHE can improve the contrast of images that are partially overexposed and/or partially underexposed.
In addition to image processing to improve image quality, image classification may also be of interest in various circumstances. For example, in printing or copying, various settings (e.g. halftone mode, color table, etc.) can be selected automatically if the image content or class of an image (e.g., text, graphic, photograph, etc.) is known.
Although AHE is relatively effective in fixing exposure problems in an image, it also introduces unwanted, tiling artifacts. In addition, if AHE is mistakenly applied to a properly exposed image, the process boosts contrast to an undesirable level and the resulting image is worse than the original. Accordingly, there is a need for improved methods and systems for processing images.